They were designed to withstand a peak overpressure of 10 pounds per square inch. Three structures survived at only a slightly greater overpressure, 11.6, while 3 identical structures failed, although they were only 500 feet closer. FIGURE 6.-Structure after a peak overpressure in excess of 11.6 pounds per square inch. Mr. HOLIFIELD. Now, what pounds per square inch did you say this structure was subjected to? Mr. VORTMAN. I do not have the pounds per square inch, but it was 500 feet closer than the shelters receiving 11.6 pounds per square inch. Now, this again is evidence of the precision with which the failure of structures can be predicted. Mr. HOLIFIELD. If these were the same type shelters, it shows what the distance of 500 feet will do in the case of identical shelters. Mr. VORTMAN. It also shows the precision at a short distance and 500 feet beyond. Mr. HOLIFIELD. Had you calculated that this structure as shownMr. VORTMAN. There were 3 stations, 1 at the design distance of 10 pounds per square inch and 1 further and 1 closer. The 1 at the design distance stood, and the 1 at the forward distance went down. This did, in fact, bracket the expected damage. Mr. HOLIFIELD. Were they 500 feet apart? Mr. VORTMAN. There was a distance of 500 feet between the first and second group, and a slightly larger distance between the second and third group. Mr. HOLIFIELD. Do you have the pounds per square inch that the third group, the farthest away, was subjected to? Mr. VORTMAN. That was about 7 pounds per square inch. Mr. HOLIFIELD. In other words, it reduced Mr. VORTMAN. They were placed for 7, 10, and 13 pounds per square inch. The design was for 10 pounds per square inch, but they were placed for 7, 10, and 13 pounds per square inch. Now, in passing, it is worth noting that some pressure did reach the inside of these structures. The peak overpressure inside the shelter was 35 percent of that outside. The structure also gave inadequate protection from radiation. Mr. HOLIFIELD. They did what? Mr. VORTMAN. They gave inadequate protection from prompt radiation. Mr. HOLLIFIELD. Do you have measurements on the external and internal radiation? Mr. VORTMAN. We have measurements of the internal radiation intensity and the measurements of the outside were taken from three free-field measurements and interpolated between points of measurements at various distances. Mr. HOLIFIELD. Could you give us the relative reduction of those two, the external to the internal, so we could get an idea of how much protection was afforded by the structure? Mr. VORTMAN. I can give you that only for the prompt gamma. The ratio of the incident to the average inside was ranged between 112 and 2.8 so that it was a factor between 12 and 3 reduction. Mr. HOLIFIELD. What thickness were the walls of that structure? Mr. VORTMAN. I believe they were either 6 or 8 inches. They were 8 inches. Mr. HOLIFIELD. Would a wooden door have anything to do with the high incidence inside? Mr. VORTMAN. It probably had something to do with it. The wooden door, however, was not facing the source of the blast, it was side on to the blast. Mr. HOLIFIELD. It would nevertheless be a factor of gamma penetration; would it not? Mr. VORTMAN. It certainly would. Mr. HOLIFIELD. It would contribute to a higher incidence inside? Mr. VORTMAN. Yes. Mr. HOLIFIELD. Did you have wooden doors in all instances? Mr. VORTMAN. Yes; in each of these nine cases there were wooden doors. Mr. HOLIFIELD. What was the reason for having wooden doors there in place of cement doors? Mr. VORTMAN.. In place of concrete doors? Mr. HOLIFIELD. Yes. Mr. VORTMAN. I think it was a matter of construction simplicity. If these were to be used by a family concrete doors would certainly increase the cost and the wooden doors did reduce, as I have indicated-did reduce the blast overpressure inside to about one-third of that outside, so they served an effective purpose in that sense. Mr. HOLIFIELD. Yes; but if the incidence was still too high inside for safety, your economics defeated your purpose of the shelter. Mr. CORSBIE. Mr. Chairman, partly in explanation, these tests were conducted on a shot of declassified yield and it was between 30 and 35 kilotons on a 500-foot tower so to get the overpressures then from that relatively low yield you had to come into a higher range of prompt radiation. For a higher yield weapon, it might achieve this resistance to the overpressures, but be at such distance as to have a much lower radiation. Mr. HOLIFIELD. I do not understand the pertinance of your remarks because it would seem to me that if I were testing a structure of that type I would test it with both cement doors and wood doors because the rest of your structure was cement. Mr. CORSBIE. It would have been a good idea. Mr. HOLIFIELD. I do know that you did have some heavy metal doors there on some other types of structures. Mr. CORSBIE. That was in Plumbbob. This was in 1955. This was really a test against blast and not radiation. Mr. HOLIFIELD. I see. Proceed. Mr. VORTMAN. Another dual-purpose above-ground shelter was a reinforced-concrete bathroom shelter designed to withstand 5 pounds per square inch. The bathroom of an ordinary 1-story rambler house was built with 8-inch-thick reinforced-concrete walls, ceiling, and floor. Blast-resistant door and window shutters were provided. The exterior is shown in the next slide (fig. 7). Before the shot. This shows only the outside of the house with the shutter in place. The following slide (fig. 8) shows the same view from the outside with the shutter having been opened. The house was completely demolished. The glass in the inside window was not broken at 5 pounds per square inch, so that was satisfactorily protected by the blast shutter. |